BIODIVERSITY Sum total of diversity that exists at all levels of biological organisation.
o Levels of biodiversity –> Genetic, Species and Ecosystem levels
2. GENETIC DIVERSITY:
o A single species might show high diversity at the genetic level over its distributional range.
o India has more than 50,000 genetically different strains of rice, and 1,000 varieties of mango.
3. SPECIES DIVERSITY:
o The diversity at the species level.
o For example, the Western Ghats have a greater amphibian species diversity than the Eastern Ghats.
4. ECOLOGICAL DIVERSITY:
o At the ecosystem level, India, with its deserts, rain forests, mangroves, coral reefs, wetlands, estuaries, and alpine meadows has a greater ecosystem diversity than a Scandinavian country like Norway.
5. More than 1.5 million species have been recorded in the world, but there might still be nearly 6 million species on earth waiting to be discovered and named.
o Of the named species, > 70 per cent are animals, of which 70 per cent are insects. www.biomentors.online
o The group Fungi has more species than all the vertebrate species combined.
6. India has only 2.4 per cent of the world’s land area, its share of the global species diversity is 8.1 per cent.
o India, with about 45,000 species of plants and twice as many species of animals,
o Among one of the 12 mega diversity countries of the world.
PATTERNS OF BIODIVERSITY
7. Latitudinal gradients:
●SPECIES DIVERSITY DECREASES AS WE MOVE AWAY FROM THE EQUATOR TOWARDS THE POLES.
●Tropics (latitudinal range of 23.5° N to 23.5° S) has more species than temperate or polar areas.
8. India, with much of its land area in the tropical latitudes, has more than 1,200 species of birds.
9. Tropical Amazon rain forest in South America has the greatest biodiversity on earth.
10. SPECIES RICHNESS OF THE TROPICS IS MORE BECAUSE:
●Tropics had more evolutionary time;
● They provide a relatively constant environment (less seasonal variation than temperate zone) and,
●They receive more solar energy which contributes to greater productivity.
11. German naturalist and geographer Alexander von Humboldt observed that within a region species richness increased with increasing explored area, but only up to a limit. (species -area relationship) In fact, the relation between species richness and area for a wide variety of taxa (angiosperm plants, birds, bats, freshwater fishes)
TURNS OUT TO BE A RECTANGULAR HYPERBOLA.
12. It is believed that communities with high diversity tend to be less variable, more productive and more resistant to biological invasions.
13. In his outdoor experiment, Tilman found that plots with more species showed less year-to-year variation in total biomass. www.biomentors.online
14. RIVET POPPER HYPOTHESIS WAS GIVEN BY PAUL EHRLICH.
● It explains the importance of biodiversity for ecosystem.
● Through this hypothesis he tried to explain the importance of biodiversity in a ecosystem.
LOSS OF BIODIVERSITY:
15. The IUCN Red List (2004) documents the extinction of 784 species (including 338 vertebrates, 359 invertebrates and 87 plants) in the last 500 years.
16. SOME EXAMPLES OF RECENT EXTINCTIONS include the
o Dodo (Mauritius),
o Quagga (Africa),
o Thylacine (Australia),
o Steller’s Sea Cow (Russia) And
o Three Subspecies (Bali, Javan, Caspian) Of Tiger.
17. The last twenty years alone have witnessed the disappearance of 27 species.
18. some groups like amphibians appear to be more vulnerable to extinction.
19. More than 15,500 species world-wide are facing the threat of extinction. Presently, 12 per cent of all bird species, 23 per cent of all mammal species, 32 per cent of all amphibian species and 31per cent of all gymnosperm species in the world face the threat of extinction.
20. Loss of biodiversity in a region may lead to
o Decline in plant production,
o Lowered resistance to environmental perturbations such as drought
o Increased variability in certain ecosystem processes such as plant productivity, water use, and pest and disease cycles.
CAUSES OF BIODIVERSITY LOSSES
21. THERE ARE FOUR MAJOR CAUSES (‘THE EVIL QUARTET’) OF BIODIVERSITY LOSS
o HABITAT LOSS AND FRAGMENTATION:
This is the most important cause driving animals and plants to extinction.
The most dramatic examples of habitat loss come from tropical rain forests.
Once covering more than 14 per cent of the earth’s land surface, these rain forests now cover no more than 6 per cent.
THE AMAZON RAIN FOREST (‘LUNGS OF THE PLANET’) harbouring probably millions of species is being cut and cleared for cultivating soya beans or for conversion to grasslands for raising beef cattle.
When large habitats are broken up into small fragments due to various human activities, mammals and birds requiring large territories and certain animals with migratory habits are badly affected, leading to population declines. www.biomentors.online
o OVER-EXPLOITATION:
Over-exploitation of natural resources damages biodiversity
Many species extinctions in the last 500 years (Steller’s sea cow, passenger pigeon) were due to overexploitation by humans.
Presently many marine fish populations around the world are over harvested, endangering the continued existence of some commercially important species.
o ALIEN SPECIES INVASIONS:
When alien species are introduced unintentionally or deliberately some of them turn invasive, and cause decline or extinction of indigenous species.
The Nile perch introduced into Lake Victoria in east Africa led eventually to the extinction of an ecologically unique assemblage of more than 200 species of cichlid fish in the lake.
Invasive weed species like carrot grass (Parthenium), Lantana and water hyacinth (Eicchornia) are dangerous threat to native species of India.
The recent illegal introduction of the African catfish Clarias gariepinus for aquaculture purposes is posing a threat to the indigenous catfishes in our rivers.
o CO-EXTINCTIONS:
When a species becomes extinct, the plant and animal species associated with it in an obligatory way also become extinct.
When a host fish species becomes extinct, its unique assemblage of parasites also meets the same fate.
Another example is the case of a coevolved plant-pollinator mutualism where extinction of one invariably leads to the extinction of the other.
BIODIVERSITY CONSERVATION
22. The reasons for conserving biodiversity are
o Narrowly utilitarian,
o Broadly utilitarian and
o Ethical.
23. THE NARROWLY UTILITARIAN REASONS
o it refers to those part of diversity from which human derive direct benefits
o humans derive countless direct economic benefits from nature food (cereals, pulses, fruits), firewood, fibre, construction material, industrial products (tannins, lubricants, dyes, resins, perfumes) and products of medicinal importance.
o More than 25 per cent of the drugs currently sold in the market worldwide are derived from plants and 25,000 species of plants contribute to the traditional medicines used by native peoples around the world.
o With increasing resources put into ‘BIOPROSPECTING’ (exploring molecular, genetic and species-level diversity for products of economic importance), nations endowed with rich biodiversity can expect to reap enormous benefits.
24. THE BROADLY UTILITARIAN REASONS
o It refers to general use of biodiversity
o Biodiversity plays a major role in many ecosystem services that nature provides.
o There are many indirect benefits we receive through ecosystem services such as pollination, pest control, climate moderation and flood control.
o The fast dwindling Amazon forest is estimated to produce, through photosynthesis, 20 per cent of the total oxygen in the earth’s atmosphere.
25. THE ETHICAL REASONS
o Every species has an intrinsic value, even if it may not be of current or any economic value to us. www.biomentors.online
o We have a moral duty to care for their well-being and pass on our biological legacy in good order to future generations.
26. Biodiversity conservation may be in situ as well as ex situ.
27. IN SITU CONSERVATION:
● The endangered species are PROTECTED IN THEIR NATURAL HABITAT so that the entire ecosystem is protected in situ conservation.
● Recently, 34 ‘biodiversity hotspots’ in the world have been proposed for intensive conservation efforts.
● Of these, three (Western Ghats-Sri Lanka, Himalaya and Indo-Burma) cover India’s rich biodiversity regions.
● Although all the biodiversity hotspots put together cover less than 2 percent of the earth’s land area, the number of species
●they collectively harbour is extremely high and strict protection of these hotspots could reduce the ongoing mass extinctions by almost 30 per cent.
● Our country’s in situ conservation efforts are reflected in its 14 biosphere reserves, 90 national parks, 448 wildlife sanctuaries and many sacred groves.
●Sacred groves (large of forest where all the trees and wildlife within were respected and given total protection) are found in Khasi and Jaintia Hills in Meghalaya, Aravalli Hills of Rajasthan, ●Western Ghats regions of Karnataka and Maharashtra and the Sarguja, Chanda and Bastar areas of Madhya Pradesh. In Meghalaya, the sacred groves are the last refuges for a large number of rare and threatened plants.
28. EX SITU CONSERVATION:
● In Ex situ conservation, threatened animals and plants are taken out from their natural habitat AND PLACED IN SPECIAL SETTING WHERE THEY CAN BE PROTECTED AND GIVEN SPECIAL CARE.
●Ex situ conservation methods include
•protective maintenance of threatened species in zoological parks and
•botanical gardens,
•in vitro fertilisation,
•tissue culture propagation and
•cryopreservation of gametes.
29. THE HISTORIC CONVENTION ON BIOLOGICAL DIVERSITY (‘THE EARTH SUMMIT’) HELD IN RIO DE JANEIRO IN 1992, CALLED UPON ALL NATIONS TO TAKE APPROPRIATE MEASURES FOR CONSERVATION OF BIODIVERSITY AND SUSTAINABLE UTILISATION OF ITS BENEFITS.
o In a follow-up, the WORLD SUMMIT ON SUSTAINABLE DEVELOPMENT held in 2002 in Johannesburg, South Africa, 190 countries pledged their commitment to achieve by 2010, a significant reduction in the current rate of biodiversity loss at global, regional and local levels.
